Electrostatics is concerned with the electrical fields and scalar potentials of stationary electrical charges and charge distributions. Use this for questions about electromagnetic situations in which currents and magnetic fields are absent, otherwise use [tag:electromagnetism] and/or ...

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6answers
85 views

When we write that $F = -\nabla V$ , what would happen if we ommit the (-) minus sign

I have had this question for a long time. In classical mechanics, if we choose $\mathbf F = -\mathbf \nabla \, V,$ with the minus sign, we can proof the work - kinetic energy theorem. What are the ...
0
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0answers
9 views

Finding the value of E at a point in a 3D field with 2 separate point charges

Having some trouble with this question: A charge 30 nC is situated at the point (x, y, z) = (0, 2, 0) and a charge of –30 nC at the point (0, -2, 0) m. Find E at the points: (a) A = (4, 2, 4) m
0
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1answer
41 views

Saving energy while charging capacitor

While charging a capacitor by a DC source, half energy is wasted as heat. Can't we save that energy? Here I am talking about $$1/2CV^2 $$ which is wasted while supplying $$CV^2$$
0
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2answers
28 views

Some Clarifications about Electricity

In the diagram below (ignoring the text), does the $V$ mean that there is some electric field outside of this system which results in a potential difference of $V$ between $a$ and $b$ or does it mean ...
1
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0answers
28 views

Coulombs Law on Quarks [on hold]

As from opinion from others the question don't seem to be clear so I did some changes. What is 5.33... it is 5+0.3+0.03+0.003+.... this sequence does not ends. now if we have a ball and we need to ...
0
votes
3answers
41 views

Is it possible to avoid static electricity? [on hold]

Sometimes I touch a car or a door and I feel the static electricity in my hand and it hurts sometimes. I try not to touch anything because I feel like I am going to feel this pain again. Is there a ...
0
votes
1answer
119 views

potential inside a cylindrical shell in terms of the surface potential?

Given a potential distribution $V(\phi)$ at the surface of an infinite cylindrical shell, is there an easy way to derive the potential inside the cylinder. No charges or currents anywhere.
1
vote
2answers
27 views

Why is the electric potential of a point from a point charge of +Q positive?

According to the formula, $$V = - \int \vec E \cdot d\vec r.$$ The electric potential of a point charge is $\frac{KQ}R$? However, when I perform the integration, my answer is $-\frac{KQ}R$. Since ...
0
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2answers
1k views

Meaning of boundary condition for steady current density?

Although I understand the derivation of boundary condition in case of steady electric current but I did not understand, that the electric field which is in direction of $J$ current density that is ...
1
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2answers
44 views

How does a point charge interact with a Gaussian surface?

A spherical Gaussian surface encloses a point charge $q$. The point charge is moved to to a point away from the center of the sphere. Does the electric field at a point on the surface change? ...
1
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0answers
35 views

How did I get these strange electric shocks? [on hold]

While doing experiment on designing & fabricating temparature controller circuit using a thermistor, this strange thing happened.Me & my friend frequently experienced short pulses of electric ...
1
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2answers
76 views

Shouldn't atoms of the same element repel each other? [on hold]

Shouldn't the same type of atoms repel each other due to electrostatic charge?
0
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1answer
30 views

Why is resistance equal to the Voltage over the flowing current? [on hold]

I can never understand these types of questions: questions based on definitions. So resistivity of a substance is defined as the voltage provided over the current flowing. But, my first question: ...
10
votes
2answers
593 views

Why does electric force depend on the medium?

Comparing the equations for the gravitational and electric force $$\vec{F}_g=-\frac{Gm_1m_2}{r^2}$$ and $$\vec{F}_e=\frac{Kq_1q_2}{r^2}$$ I noticed the only major difference between them is that ...
2
votes
1answer
45 views

Electric Potential due to Sphere when cavity is at arbitrary position [on hold]

While doing practice question, I came across a question... A solid sphere of radius a has a cavity of radius b which has a uniformly charge distributed with density $-\rho$ and the remaining part ...
0
votes
2answers
25 views

How is electric field effected by loss of energy of charge?

Recently, I asked a question related to energy of a charge(This is the question). In one of the answers, in the comments section, I got an answer that the strength of the electric field is lessened ...
2
votes
1answer
142 views

Physical interpretation related to a non-linear partial differential equation

I am doctoral student in pure mathematics working on a particular problem. My question is if this problem has applications to real world phenomena. I will try to explain the direct problem starting ...
1
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1answer
134 views

Is putting a charged balloon up to a neutral wall polarization AND temporary induction, or just polarization?

Is putting a balloon that is charged up against a wall and having it stick polarization AND charging by temporary induction, or just polarization?
0
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3answers
360 views

Why may an air passenger experience an electric shock when he touches the door knob of the toilet of an aeroplane flying at a high altitude?

Why may an air passenger experience an electric shock when he touches the door knob of the toilet of an aeroplane flying at a high altitude?
3
votes
3answers
49 views

If the entire potential energy of the charge is lost within the circuit, what happens to the charge?

This is a really confusing question for me. Suppose, there is an electric circuit. And, right near to the negative terminal of the battery, I place 3 bulbs, which would take almost all the energy of ...
2
votes
4answers
192 views
+50

What will be final velocity of three charges $q$, $q$, $2q$?

What will be final velocity of three charges q, q and 2q kept along an eqilateral triangle of side r at infinite distance. All three masses are equal. I tried to conserve Total Energy ...
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0answers
21 views
1
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2answers
174 views

Two charged spheres connected with a conductor

I have a problem with a electrostatics problem: there are two spheres, each one of the same size carrying the same amount of charge, but of different sign. They are connected by a conducting wire, ...
1
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1answer
39 views

Figuring out the orientation of a dipole and its distance from a point charge

The problem assigned is this: A dipole is centered at the origin of a coordinate system, and a small charged sphere is some distance away along the perpendicular bisector of the dipole. The particle ...
0
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1answer
67 views

Two concentric conducting shells connected by wire with modified Coulomb law?

This question is related to this one, but is a bit different. Consider two concentric and conducting spherical shells connected by a wire. Inner shell has radius $b$ and (unknown) charge $q_b$ while ...
2
votes
0answers
44 views

Gauss' Law and Electric Field Close to a Ball

So I've learned about Gauss' law and I have something in my head. Why does electric field that is very close to a ball is not close to infinity. Take a look at this image: As we can see, if we make ...
1
vote
1answer
28 views

boundary condition of electrical field

The boundary condition of electrical field is well known. $$ E^{\perp} _{above} -E^{\perp} _{below} = \frac{\sigma}{\epsilon_0}$$ Griffiths wrote that where there is no surface charge $E^{\perp}$ is ...
2
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2answers
3k views

The electric field of a conductive sphere containing a charge - grounded vs not grounded

Let's suppose we have a sphere but unlike theoretical ones it'll have some thickness say $\Delta r$ and inner radius $R$. What I was wondering about is how will it behave if we place some charge $q$ ...
3
votes
2answers
98 views

Charging by induction [closed]

When we charge an conductor by induction and grounding, we first bring a negative charge to the conductor. As a result the mobile electrons of the conductor get repelled and stay far from the negative ...
1
vote
2answers
312 views

Should the electric potential of a positively charged sphere be negative?

Because the indefinite integral of the electric field results in a negative value? (As the function is proportional to $r^{-2}$? I've got to be missing something... Help please!! Thanks! Also, I ...
0
votes
1answer
4k views

Potential energy of the dipole-dipole interaction for two parallel dipole moments

I am looking for an equation that gives me the potential energy of the interaction between two parallel dipoles.
-1
votes
0answers
24 views

Problem in electrostatics [closed]

I tried a problem in electrostatics. In which I emplyed two different methods to find the electric field inside a solid cylinder of charge distribution having density ...
1
vote
2answers
61 views

Finding out the charge density (electrostatics) [closed]

A solution to the potential in the region $ -a < y <a$ , where there is charge density $\rho$ , satisfies the boundary conditions , $\phi = 0$ in the planes $ y = -a$ and $y = a$. $$ \phi = ...
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votes
0answers
25 views

Gauss law-electric field through the spherical surface of a sphere [closed]

FIND THE WORK DONE IN MOVING A POINT CHARGE Q=10 MICROCOULOUMBS FROM THE ORIGIN TO A POINT(4,pie/4,pie/2)SPHERICAL COORDINATES IN THE FIELD E=5e^(-r/4)+10/(rsinx)
1
vote
1answer
112 views

Current in discharging capacitor through fixed resistor?

In the textbook I'm using for physics it says that the charge left on the plates of a capacitor after time $t$, that is discharging through a fixed resistor, is $Q=Q_0e^{-t/\tau}$ where $\tau=RC$ is ...
0
votes
2answers
141 views

Two different electrostatic charges in rotation

It's a theoretical problem. I mean I drawn a circle and I consider this circle exist. I would like to understand how works this device composed of a circle and two charges: Two charges fixed on a ...
1
vote
0answers
25 views

Surface bound charge density in dielectric displacement

In Griffiths, it derived that the electric potential caused by Polarization $\bf {P}$ is written $$V({\bf r}) = \frac{1}{4\pi \epsilon_0} \int_{\mathcal{V}} \frac{\hat{\gamma} \cdot {\bf P}{({\bf ...
0
votes
1answer
251 views

Work done by battery and potential energy of a capacitor

I have a doubt about the work done by a battery and the potential energy of a capacitor? 1- Consider a circuit where the capacitors are connected to the terminals of a battery. Through calculations ...
0
votes
0answers
33 views

Can we generate artificial electrostatic energy? [closed]

Can we generate artificial electrostatic energy for electrostatic attraction?And can it be controlled to get element specific electrostatic attraction?
1
vote
1answer
62 views

Mass of a point charge [closed]

A point charge is defined as an electric charge at a mathematical point with no dimensions(Wikipedia: https://en.wikipedia.org/wiki/Point_particle#Point_charge). Can anything be said about its mass in ...
0
votes
1answer
36 views

Parallel plates with differing charges

I'm given a problem involving two parallel conducting plates a small distance apart. One has charge Q, the other is neutral. I'm asked to find the surface charges on all faces. I began by ...
3
votes
1answer
180 views

Determining potential in coaxial cylinders

If I have two conducting, coaxial cylinders as shown: The potential at the outer cylinder is = 0. And I apply a potential difference across both cylinders in the form $V_a - V_b = V_{ab}$, how can ...
1
vote
2answers
30 views

If protons(positive charges) also flow in a circuit, do we say that a conductor has free protons?

This might be a stupid question, but it is logical. We say that even protons or positive charge can flow to constitute current. But, protons are present inside the nucleus of an atom. So, when we say ...
2
votes
2answers
25 views

Which charge actually moves to constitute current? Positive or negative?

Now this might be a very stupid question for many readers, but I am getting really confused. I was reading about electricity and current, and I read this: Suppose we connect a wire to the ends of a ...
2
votes
0answers
22 views

Symmetry arguments and plane sheet of charge [duplicate]

The electric field due to a infinite plane sheet of charge is given by $\sigma/\epsilon_o$. Now could we have deduced by symmetry that the electric field's magnitude won't depend on distance?
4
votes
3answers
79 views

Do we know why the field produced by charge extends to infinity?

Do we have any model to show why charge field or magnetic field extends till infinity. Edit: I agree that according to coulombs law $1/r^2$ cannot be 0 but do we know why this happens.I think I am ...
0
votes
0answers
22 views

Electrostatic force of interaction between two hemispheres [closed]

We are given a hollow sphere with charge Q. Now this hollow sphere is cut into two identical hemispheres. We have to find the electrostatic force of interaction between them / force required to hold ...
3
votes
2answers
52 views

Some confusions regarding electrostatic shielding

A spherical conductor A contains two spherical cavities as shown. The total charge on conductor itself is zero. However, there is a point charge q1 at the centre of one cavity and q2 at the centre ...
1
vote
1answer
31 views

Electrostatics: Cylinder and conducting plane question (method of images)

I was looking at some problems/questions about electrostatics and came across this question: An infinitely long cylinder of radius $a$ and with charge density per unit length $\lambda$ is placed ...
2
votes
4answers
171 views

How to calculate the work of the electrostatic forces in a parallel-plate capacitor?

The expression of the energy stored in a parallel-plate capacitor is: $$U = \frac{e_0\cdot A \cdot V^2}{2d}$$ with $e_0$ the vacuum permittivity, $A$ the surface of the capacitor, $V$ the applied ...